Which two components are primarily responsible for regulating the progress through the cell cycle?

The cell cycle is a complex process that is tightly regulated to ensure that cells divide correctly and at the appropriate time. Cyclins and cyclin-dependent kinases (CDKs) are central to this regulation.

Cyclins are proteins whose levels fluctuate throughout the cell cycle; they activate cyclin-dependent kinases by binding to them, prompting the kinases to phosphorylate target proteins necessary for progression through different phases of the cell cycle. For instance, cyclins assist in transitioning from G1 to the S phase, and from G2 to mitosis, by activating specific CDKs that drive these transitions.

The activities of cyclins and CDKs are meticulously monitored through various checkpoints in the cycle, allowing the cell to assess whether conditions are favorable for division, DNA is intact, and all cellular components are ready for the next stage. This system prevents uncontrolled cell division which could lead to cancerous growths.

The other choices do not play a direct role in regulating the cell cycle. Chromosomes and centromeres are structural components involved in the segregation of genetic material during cell division, but they do not regulate the cycle itself. Ribosomes and mitochondria are involved in protein synthesis and energy production, respectively, and DNA and RNA are essential for genetic